Attachment for chasing threads on horizontal lathes



Jan. l5, 1963 DON PIETRO clccARELLl 3,073,194

ATTACHMENT FOR CHASING THREADS oN HORIZONTAL LATHEs Filed April 6, 1956a" J "6 1 f l if mm2 l: l; iT5 7 la. f

5 9* /2 9( .qui-V y d lum 9 United States Patent iltice l A3,073,194Patented Jan. 15, 1963 3,073,194 ATTACHMENT FOR CHASING THREADS NHORIZONTAL LATHES Don Pietro Ciccarelli, Turin, Italy, assigner toIstituto Salesiano Rebaudengo, Turin, Italy Filed Apr. 6, 1956, Ser. No.576,565 Claims priority, appication Italy Apr. 8, 1955 3 Claims. (Cl.82-5) This invention concerns an attachment for chasing threads onhorizontal lathes, and relates particularly to an attachment of the typedescribed in British Patent 764,926, which includes a feed camdetermining the pitch of cutting and driven by means of a telescopictransmission rod from the lathe feed shaft, said transmission rod beingprovided with at least one universal joint to operate a longitudinaltool carriage in opposition to spring arrangements adapted automaticallyto restore said carriage to its initial position at the end of itsworking stroke, and a second cam mounted coaxially of and rotating withthe iirst cam to effect disengagement of the tool from the workpiece atthe end of its working stroke in opposition to spring arrangements on atransverse carriage, and to bring the tool back to its initial positionautomatically at the start of a succeeding cutting operation, therequired transverse feed of the tool on the transverse slide beingcontrolled by hand by the operator. In one embodiment of the. attachmentabove referred to, the second cam operates a lever pivotal about a fixedpoint in order to move the transverse carrage so as to disengage thetool from the workpiece.

' lt is an object of the present invention to ettect advance of thetransverse carriage automatically during the return stroke of thelongitudinal carriage, through the medium of a controllable deviceacting on said transverse carriage in dependence upon the movement ofthe longitudinal carriage.

Another object of the invention is to effect outward and inward motionof the tool with respect to the workpiece, not by a lever pivotal abouta iixed point, but by an oblique lever integral with the longitudinaltool carriage and operated by a bar sliding in said longitudinalcarriage so as to act at the appropriate moment on a pin integral withthe transverse tool carriage.

These and other objects of the invention will become more apparent inrelation to three preferred forms of construction, given by way ofexample only and in no way intended to limit the scope of the invention,described with reference to the accompanying drawings, in which:

FIG. 1 is a longitudinal cross-sectional view taken on the line I-I ofFIG. 3 showing la rst form of construction of the attachment,

FIG. 2 is a side elevation of said attachment partly in section showingthe auotmatic advancing device of the transverse carriage,

FIG.V 3 is a plan View, partly in section, of the attachment illustratedin the preceding iigures,

FIG. 4 is a cross-section taken on the line IV-IV of FIG. 2.

With reference to the form of construction of improved cutting device asshown in FIGS. 1 to 4, 1 is the end of a telescopic transmission rod orshaft provided with a universal joint la, which rod is driven by thefeed shaft of the lathe, as described in British Patent 764,926, andtransmits rotary motion via a worm, not shown, engaged with the gear 2to a pin or shaft 3 piv- Oted on the longitudinal carriage 1b. Shaft 3has a cam 4 removably iixed thereto, which, at the furthest point fromthe centre of the pin 3 has a catch or second cam surface 4a, which isan extension which projects outward and sidewards relative to cam 4 asbest seen in sion rod 1 and the cam 4 as also decribed in Britih PatentThe catch 4a operates through a bearing wheel 8 on the end of a slidingbar 9, guided for translation by and between a pair of parallel guides9a mounted on the slide 6, and positioned parallel to the direction ofsliding thereof. The opposite end of bar 9 is provided with an obliquegroove or guideway 9b into which slidably iits a slide or follower 10ixed on the transverse carriage 7 by means of a threaded pin 11. Theslide 6 has a cavity between the two parallel guides 9a and this is usedfor housing a compression spring 12, one end of which bears on an end ofsaid cavity, that is, the left end as the parts are viewed upon FIGURESl and 3, and faces the direction of motion of the transverse carriage,whilst the other end of said spring abuts the iiattened side surface ofa pin 9c integral with bar 9. The catch or second cam surface 4a of cam4 effects, therefore, translation of the shaft 9 toward the left at theend of the travel of cutting tool, and, consequently, the disengagementof the tool from the workpiece by motion of the slide 10 in the obliquegroove 9b; the spring 12 which becomes compressed during this slidingmotion provides for the return of bar 9 towards the right after thepoint of the catch 4a rotating with cam 4 has passed the bearing wheel8, said spring thus also controlling the consequent return to thestarting position of the slide 10 and of the transverse carriage 7integral with it. The catch 4a is provided with a slope so formed thatthe approach of the cutting tool to the workpiece takes place after thelongitudinal carriage, shifted to the left by the cam 4, has beenbrought into the starting position by restoring spring 13 securedbetween the bed and the carriage and acting on said carriage.

The automatic advancing device of the cutting tool for successivecutting operations is enclosed in a box which is carried by siide 6 andthe details of which are shown in FIGS. 2, 3 and 4. On the front end ofthe transverse carriage there is iitted a 'push-rod 14, FIG. 4,co-acting with an eccentric cam 15a integral with a shaft 15 parallel tothe direction of sliding motion of slide. Said shaft 15 at its oppositeend has a bevel pinion 16 geared with another bevel pinion 17 journaledon a bearing pin 18. This latter pinion 17 -is connected to a disc 19provided with teeth on part of its circumference. The same pin 18 actsas a pivot for a right-angular plate 20. A moving catch 21 is pivotallymounted on a plate which is connected to plate 20 and positioned toengage an extension 20a of the intermediate plate. Plate 20 is urgedinto counterclockwise rotation, as the parts are viewed upon FIG. 2 by aspring 22 and bears a pawl 23 pressed against the toothed disc 19 bymeans of a spring 24. A stop 20h limits the counter-clockwise rotationof the plate 20.

Furthermore, pin 18 acts as a pivot for a second plate 25, the ends ofwhich are bent to extend axially over the periphery of disc 19 so aspartly to cover it. The left arm of plate 25, as seen in FIG. 2, isformed as a toothed section which meshes with a pinio-n 26 operable byhand by a button 27 protruding from the box containing the device. Thelongitudinal carriage also has a stop 28, FIG. 2, to engage catch 21when the carriage moves into first position in the retrograde position.A button 29 integral with pinion 17 allows the device to be operated byhand.

The automatic advancement device functions as fol- 3. lows: At eachreturn. of the longitudinal carriage the catch 21 abuts against thefixed stop 28and pressing against the extension 20a of the plate 20,causes said plate to rotate in a clockwise direction. The pawl 23 fixedto the plate 20 and engaged with the toothed disc 19 4effects rotationofthe disc 19., which drives the pinion 17 and, through thepinon 16 andshaft 15, rotate the cam V15a` collaborating with push-rod 14. The angleof rotation of the disc 19, and` therefore also of the cam 15a can beAregulated .bymeans of button 27 acting throughthe toothed wheel26 on theplate 25. According to the position given to said plate 25 withrespectto the pawl 23, the latter, in the oscillating motion of constantamplitude of the plate 20., therefore engages with a greater or lessernumber of teeth of the disc 19 and consequently causes said disc toro-tate in a clockwise direction by a greater or lesser angle for eachstroke of the carriage. The transverse carriage which is being pressedagainst the workpiece by means `of the slide and the connecting pin -11to a degree determined by the momentary position of the cam 15awithrespect to the push-rod 14, will therefore move forward after eachreturn stroke through a distance determined by the shape of the cam. 15aand by its angle of rotation, until it has reached its maximum alloweddepth, corresponding to the position represented in FIG.,4 through the.cooperation of cam 15a.and push rod14. This position being reached i.e.the follower actionhaving been completed, the .cam V15a is caused bythe'advance device to rotate through a further vangle in aclockwisedirection as viewed upon FIG. 4, so that the push-rod 14 engages vin theextensiongof tsaidcam, so impeding the cutting tool from approaching theworkpiece. In4 addition to this, the disc 19 kpresents to the pawl 23,its non-toothed section, andA said catch will henceV not operate. At thebeginning of the. cutting operation of the following workpiece, the`advance device is restored to the starting position with the ,aid ofthe button 29V and eventually by the button 27. suitably provided withcontrol notches.v

The mechanism describedy can be utilised either for internal or externalthread cutting, while permitting the latheitself to be `utilised forconventional turning operations..r

In practice, such details of construction as dimensions, materials, theshape and. the like of the device, may be varied without departing fromthe scope of the invention as defined in the appended claims. Thus, forexample, in order to facilitate the sliding movements of-the carriagesthere. can be used straight and inverted superpcsed V-shaped guides .inwhich are arranged cylindrical rollers with .theirshafts askew andYreciprocally olf-set at 90, said rollers running freely betweensaidguides.

Iclaim: Y

1. A .threading attachmentr for a lathe adapted to mount and rotate aworkpiece about a first longitudinal axis, a carriage, a slidemounted'on -said carriage for guided translation parallel. withsaidfirst axis, a bar mounted Y Y on said slide for guided translationrelatively thereto parallel rwith said first axis, a tool carriermounted .on saidY Slide for -guidedtranslation toward .and from saidfirstl axis, a pin-and-slot connection between said bar andv,toolcarrier and operating to translatevsaid tool carrier by V.and inresponse ,to translationV of saidbar, arst cam journaled on saidcarriage,vsaid first cam having a first surfaceengaging and`:translating said slide in a work p and rotate a workpiece about afirst longitudinal axis,

stroke. said first cam also having a second surface engaging said bar ata predetermined rotational position of said first cam, to therebyretract said tool carrier from said first axis, spring means betweensaid slide and bar urging said tool carrier toward said first axis, asecond cam journaled on said slide on a second axis parallel with saidfirst axis, a follower fixed with said to l carrier and urged intoengagement with said second cam by said spring means, means responsiveto retrograde translation of said slide when released by said first cam,to rotate said second cam and thereby free said tool carrier to measuredadvancement toward said first axis by said spring means, and meansurging said slide into retrograde translation.

2. A threading attachment for a lathe adapted to mount a carraige, aslide mounted on said carriage for guided translation parallel with saidfirst axis, a bar mounted on said slide for guided translationrelatively thereto parallel with said first axis, a tool carrier mountedon said slide for guided translation toward and from said rst axis, apin-and-slot connection between said bar and'tool carrier and operatingvto translate said tool carrier by and in responsel to translation ofsaid bar, a first cam journaled on said carriage, said first cam havinga first surface engaging and translating said slide in a workstroke,said rst cam also having a second surface engaging said Abar at apredetermined rotational position of said first cam, to thereby retractsaid tool carrier from said first axis, spring means between said slideand bark urgingsaid tool carrier toward said first axis, a seco-nd camjournaled on said slide on a second axis parallel with said first axis,a follower fixed with said tool carrier and urged into engagement withsaid second cam by said spring means, meansurgingsaid slide intoretrograde translation, a toothed disc journaled on said slide andconnected to rotate said second cam, pawl means engageable with theteeth of said disc to rotate the same, a stop fixed with said carriage,and an abutment carried byV said pawl means, said abutment engaging saidstop during retrograde translation ofsaid slide when released by saidtrst cam, to rotate said dise and second cam, thereby to free said toolcarrier to measured advancement toward said first axis by said springmeans.

3. A thread cutting attachment as in claim 2, and means manuallyadjustable to vary the angle of rotation of said disc effected by saidpawl means, foreach retrograde stroke of said slide.

References Cited in the file of this patent UNITED STATES PATENTS

1. A THREADING ATTACHMENT FOR A LATHE ADAPTED TO MOUNT AND ROTATE AWORKPIECE ABOUT A FIRST LONGITUDINAL AXIS, A CARRIAGE, A SLIDE MOUNTEDON SAID CARRIAGE FOR GUIDED TRANSLATION PARALLEL WITH SAID FIRST AXIS, ABAR MOUNTED ON SAID SLIDE FOR GUIDED TRANSLATION RELATIVELY THERETOPARALLEL WITH SAID FIRST AXIS, A TOOL CARRIER MOUNTED ON SAID SLIDE FORGUIDED TRANSLATION TOWARD AND FROM SAID FIRST AXIS, A PIN-AND-SLOTCONNECTION BETWEEN SAID BAR AND TOOL CARRIER AND OPERATING TO TRANSLATESAID TOOL CARRIER BY AND IN RESPONSE TO TRANSLATION OF SAID BAR, A FIRSTCAM JOURNALED ON SAID CARRIAGE, SAID FIRST CAM HAVING A FIRST SURFACEENGAGING AND TRANSLATING SAID SLIDE IN A WORK STROKE, SAID FIRST CAMALSO HAVING A SECOND SURFACE ENGAGING SAID BAR AT A PREDETERMINEDROTATIONAL POSITION OF SAID FIRST CAM, TO THEREBY RETRACT SAID TOOLCARRIER FROM SAID FIRST AXIS, SPRING MEANS BETWEEN SAID SLIDE AND BARURGING SAID TOOL CARRIER TOWARD SAID FIRST AXIS, A SECOND CAM JOURNALEDON SAID SLIDE ON A SECOND AXIS PARALLEL WITH SAID FIRST AXIS, A FOLLOWERFIXED WITH SAID TOOL CAR-